Access systems, such as motorized lifts, have been used to transport people and cargo. These access systems include platforms, ramps, moving seats, movable steps, and the like, which may be attached to stationary structures, such as buildings and loading docks, or mobile structures such as vehicles. Access systems have been used to provide disabled individuals access to structures that traditionally were accessible only via steps or stairs, or required an individual to step over or across an obstacle. For example, motorized lifts have been used to allow disabled individuals to enter and exit vehicles. In another example, motorized lifts have been used to load and/or unload stretchers from vehicles, such as ambulances. Motorized lifts have also been used on loading docks and trucks to allow cargo to be loaded, unloaded or otherwise moved.
When an access system is installed in a vehicle, it is generally integrated with the power sliding door system of the vehicle. The power sliding door system opens or closes the door when it receives a request to do so (a “door operation request”). The power sliding door system further includes a body control unit, door control unit, receiver, door switch and data bus. The body control unit, door control unit, receiver and door switch are all in communication with the vehicle's data bus, which enables body control unit, door control unit, receiver and door switch to communicate with each other and to receive a signal from a user indicating that the user wants to open or close the door (a “door operation request”). Generally, the user may communicate a door operation request to the power system door system by pulling on a door handle of the vehicle or pushing a button on a keyless entry device. If the door operation request is produced by a remote device, the power sliding door system receives the door operation request via the receiver. If the door operation request is produced by movement of the door handle, the door operation request causes the door switch to close, which communicates the door operation request to the power sliding door system.
When a door operation request received by the power sliding door system, it is initially received by the body control unit. The body control unit evaluates whether it is an appropriate time to operate the door. For example, the body control unit may receive signals via the data bus indicating the status of the transmission position, speed and door lock position of the vehicle. If the body control unit determines that the status of the vehicle are acceptable, the body control unit communicates a command to operate the door (a “door operation command”) to the motors and switches that unlatch the door and either open or close the door.
Access systems are installed in vehicles with a power sliding door system as described above, so that the operation of the ramp by the access system and operation of the door by the power sliding door system do not interfere with each other. To prevent such interference, the access system may be installed so that it receives the door operation commands from the body control unit. The access system will only communicate the door operation command when it determines that the ramp is fully stowed. This method requires the access system to be in communication with the data bus of the power sliding door system, either directly or through a gateway. However, vehicle manufacturers are becoming less willing to allow access systems to communicate with the data bus and thus, unwilling to allow access systems to be installed and operate in the manner described above.